Data storage device independently driving outer and inner fine actuators

ABSTRACT

A data storage device is disclosed comprising a plurality of disks each comprising a top disk surface and a bottom disk surface. A plurality of inner actuator arms each comprise a first inner fine actuator configured to actuate a top head over one of the top disk surfaces and a second inner fine actuator configured to actuate a bottom head over one of the bottom disk surfaces. A first outer actuator arm comprises a first outer fine actuator configure to actuate a top head over a top disk surface of a top disk, and a second outer actuator arm comprises a second outer fine actuator configured to actuate a bottom head over a bottom disk surface of a bottom disk, wherein the inner fine actuators are controlled independent from the outer fine actuators.

BACKGROUND

Data storage devices such as disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the actuator arm as it seeks from track to track.

FIG. 1 shows a prior art disk format 2 as comprising a number of servo tracks 4 defined by servo sectors 6 ₀-6 _(N) recorded around the circumference of each servo track. Each servo sector 6 _(i) comprises a preamble 8 for storing a periodic pattern, which allows proper gain adjustment and timing synchronization of the read signal, and a sync mark 10 for storing a special pattern used to symbol synchronize to a servo data field 12. The servo data field 12 stores coarse head positioning information, such as a servo track address, used to position the head over a target data track during a seek operation. Each servo sector 6 _(i) further comprises groups of servo bursts 14 (e.g., N and Q servo bursts), which are recorded with a predetermined phase relative to one another and relative to the servo track centerlines. The phase based servo bursts 14 provide fine head position information used for centerline tracking while accessing a data track during write/read operations. A position error signal (PES) is generated by reading the servo bursts 14, wherein the PES represents a measured position of the head relative to a centerline of a target servo track. A servo controller processes the PES to generate a control signal applied to a head actuator (e.g., a voice coil motor) in order to actuate the head radially over the disk in a direction that reduces the PES.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art disk format comprising a plurality of servo tracks defined by servo sectors.

FIG. 2A shows a data storage device in the form of a disk drive according to an embodiment comprising a plurality of disks each comprising a top disk surface and a bottom disk surface.

FIG. 2B shows an embodiment wherein a plurality of inner actuator arms each comprise a first inner fine actuator configured to actuate a top head over one of the top disk surfaces and a second inner fine actuator configured to actuate a bottom head over one of the bottom disk surfaces, and top and bottom outer actuator arms each comprising an outer fine actuator configured to actuate a top head over a top disk surface of the outer top disk, and a bottom head over a bottom disk surface of the outer bottom disk.

FIG. 2C shows an embodiment wherein the fine actuator for a top head is mechanically equivalent to the fine actuator for a bottom head resulting in opposite radial movements in response to a common control signal due to their flipped orientation relative to the top and bottom disk surfaces.

FIG. 3 shows an embodiment wherein a fine driver generates a control signal that is concurrently applied to the fine actuators of either the inner actuator arms or the outer actuator arms.

FIG. 4 shows control circuitry according to an embodiment for applying the control signal to the fine actuators of either the inner actuator arms or the outer actuator arms.

FIG. 5A shows an embodiment wherein a first fine drive controls the fine actuators of the inner actuator arms and a second fine drive concurrently controls the fine actuators of the outer actuator arms.

FIG. 5B shows an embodiment wherein the control signal generated by a fine actuator may be inverted in order to concurrently actuate the fine actuators of top and bottom disk surfaces.

DETAILED DESCRIPTION

FIGS. 2A and 2B show a data storage device in the form of a disk drive according to an embodiment comprising a plurality of disks 16 ₁-16 _(N) each comprising a top disk surface and a bottom disk surface. A plurality of inner actuator arms 18 ₁-18 _(N) each comprising a first inner fine actuator (e.g., 20 ₁) configured to actuate a top head (e.g., 22 ₁) over one of the top disk surfaces and a second inner fine actuator (e.g., 20 ₂) configured to actuate a bottom head (e.g., 22 ₂) over one of the bottom disk surfaces. A first outer actuator arm 24 ₁ comprises a first outer fine actuator 26 ₁ configure to actuate a top head over a top disk surface of a top disk, and a second outer actuator arm 24 ₂ comprises a second outer fine actuator 26 ₂ configured to actuate a bottom head over a bottom disk surface of a bottom disk. A coarse actuator (e.g., VCM 28) is configured to concurrently move the actuator arms to actuate the heads over their respective disk surface, wherein the inner fine actuators are controlled independent from the outer fine actuators.

In the embodiment of FIG. 2A, the disk drive comprises control circuitry 30 configured to process read signals 32 emanating from the heads to demodulate servo sectors and generate a position error signal (PES) representing an error between the actual position of a head and a target position relative to a target data track. A servo control system in the control circuitry 30 filters the PES using a suitable compensation filter to generate a control signal 34 applied to the VCM 28 which rotates the actuator arms about a pivot in order to actuate the head radially over the disk in a direction that reduces the PES. The heads are also servoed using a fine actuator, such as a piezoelectric (PZT) actuator, configured to actuate a suspension relative to the actuator arm as shown in FIG. 2B, and/or configured to actuate the head relative to the suspension. The servo sectors may comprise any suitable head position information, such as a track address for coarse positioning and servo bursts for fine positioning. In one embodiment, the servo bursts may comprise any suitable pattern wherein at least one servo burst consists of a periodic sequence of magnetic transitions, such as an amplitude based servo pattern or a phase based servo pattern (FIG. 1).

FIG. 2C shows an embodiment of a fine actuator comprising PZT elements configured to actuate a suspension relative to an actuator arm. In this embodiment, the fine actuator for a top head (e.g., inner fine actuator 20 ₁) is mechanically equivalent to the fine actuator for a bottom head (e.g., inner fine actuator 20 ₂). In this embodiment, a bottom fine actuator and suspension is “flipped over” relative to a top fine actuator and suspension as shown in FIG. 2C such that when a control signal is concurrently applied to both the top/bottom fine actuators of an inner actuator arm it causes an opposite radial movement of the top/bottom fine actuators. In one embodiment, concurrently actuating the top/bottom fine actuators of the inner actuator arms in opposite radial directions attenuates a vibration mode of the actuator arms.

FIG. 3 shows control circuitry according to an embodiment wherein all of the fine actuators are mechanically equivalent, and the fine actuators of the bottom heads are flipped over relative to the fine actuators of the top head such as shown in FIG. 2C. A fine driver 36 generates a control signal 38 that is selectively applied (via a demultiplexer 40) to the inner fine actuators (e.g., 20 ₁ and 20 ₂) of the inner actuator arms or to the outer fine actuators (26 ₁ and 26 ₂) of the outer actuator arms. Accordingly in this embodiment, the demultiplexer 40 may be configured so that the control signal 38 concurrently drives all of the inner fine actuators, including to drive the top/bottom fine actuators in opposite radial directions so as to attenuate a vibration mode of the actuator arms. Alternatively the demultiplexer may be configured so that the control signal 38 concurrently drives the outer fine actuators (in this embodiment the top fine actuator 26 ₁ being driven in the opposite radial direction as the bottom fine actuator 26 ₂). In this embodiment, concurrently driving the inner fine actuators without driving the outer fine actuators may attenuate a disturbance that may otherwise affect the inner actuator arms. Similarly, concurrently driving the outer fine actuators without driving the inner fine actuators may attenuate a disturbance that may otherwise affect the outer actuator arms.

FIG. 4 shows control circuitry according to an embodiment for applying the control signal 38 of FIG. 3 to the fine actuators of either the inner actuator arms or the outer actuator arms. The control circuitry comprises an input stage including a digital-to-analog converter 42 for converting a digital control signal into an analog control signal 38, and a differential amplifier 44 for amplifying the analog control signal 38. Switches 46 ₁ and 46 ₂ are configured to select either the outer fine actuators or the inner fine actuators to be driven by the input stage. Switch 48 is configured to apply feedback to the differential amplifier 44 from either the outer fine actuator or the inner fine actuator driving stages (depending on which is active). When either the inner fine actuators or the outer fine actuators are not selected (inactive), the respective switch 46 ₁ and 46 ₂ is configured so that the corresponding output stage is biased to the output common mode. In the example of FIG. 4, the switches are configured such that the inner fine actuators are active (driven by the control signal 38) and the outer fine actuators are inactive (output stage biased to the output common mode).

FIG. 5A shows control circuitry according to an embodiment wherein a first fine driver 36 ₁ generates a first control signal 38 ₁ for controlling the inner fine actuators (e.g., 20 ₁ and 20 ₂) and a second fine driver 36 ₂ generates a second controls signal 38 ₂ for independently controlling the outer fine actuators 26 ₁ and 26 ₂. In one embodiment, the inner and outer fine actuators may be controlled concurrently in order to concurrently access two disk surfaces. For example, the top head may access the top disk surface of the top disk while one of the middle heads concurrently accesses one of the middle disk surfaces (top or bottom) of a middle disk. In the embodiment of FIG. 5A, the fine actuators are mechanically equivalent with the bottom fine actuators being “flipped over” relative to the top fine actuators such as shown in FIG. 2C wherein a common control signal 38 ₁ drives all of the inner fine actuators and a common control signal 38 ₂ drives both of the outer fine actuators.

In an alternative embodiment shown in FIG. 5B, the top and bottom fine actuators are configured to actuate in the same radial direction in response to a common control signal. Accordingly in this embedment, the first fine actuator 36 ₁ generates a first control signal 50 ₁ for controlling the top inner fine actuators of the middle disks, and a second control signal 50 ₂ having an opposite polarity (via inverter 52) for controlling the bottom inner fine actuators of the middle disks. Similarly, the second fine actuator generates a first control signal 54 ₁ for controlling the top outer fine actuator of the top disk, and a second control signal 54 ₂ having an opposite polarity (via inverter 56) for controlling the bottom outer fine actuator of the bottom disk. In this embodiment, the negative polarity control signals 50 ₂ and 54 ₂ are shown as being generated by inverting the corresponding positive polarity control signals 50 ₁ and 54 ₁. However, the analog inverter shown in FIG. 5B merely indicates that in one embodiment the control signals generated by each fine driver have oppositive polarity. In other embodiments, the positive/negative polarity control signals may be generated in any other suitable manner, such as by using a non-inverting amplifier and an inverting amplifier with equal gains. In addition, a similar technique of inverting the control signal for top/bottom fine actuators may be implemented in other embodiments described above, such as in the embodiment of FIG. 3, if the fine actuators are configured to actuate in the same radial direction in response to a common control signal.

Any suitable control circuitry may be employed to implement the flow diagrams in the above embodiments, such as any suitable integrated circuit or circuits. For example, the control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a data storage controller, or certain operations described above may be performed by a read channel and others by a data storage controller. In one embodiment, the read channel and data storage controller are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC). In addition, the control circuitry may include a suitable power circuit(s) and/or a suitable preamp circuit(s) implemented as separate integrated circuits, integrated into the read channel or data storage controller circuit, or integrated into a SOC.

In one embodiment, the control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the flow diagrams described herein. The instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry. In some embodiments, at least some of the flow diagram blocks may be implemented using analog circuitry (e.g., analog comparators, timers, etc.), and in other embodiments at least some of the blocks may be implemented using digital circuitry or a combination of analog/digital circuitry.

In addition, any suitable electronic device, such as computing devices, data server devices, media content storage devices, etc. may comprise the storage media and/or control circuitry as described above.

The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method, event or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described tasks or events may be performed in an order other than that specifically disclosed, or multiple may be combined in a single block or state.

The example tasks or events may be performed in serial, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed example embodiments.

While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the embodiments disclosed herein. 

1. A data storage device comprising: a plurality of disks each comprising a top disk surface and a bottom disk surface; a plurality of inner actuator arms each comprising a first inner fine actuator configured to actuate a top head over one of the top disk surfaces and a second inner fine actuator configured to actuate a bottom head over one of the bottom disk surfaces; a first outer actuator arm comprising a first outer fine actuator configured to actuate a top head over a top disk surface of a top disk; a second outer actuator arm comprising a second outer fine actuator configured to actuate a bottom head over a bottom disk surface of a bottom disk; and control circuitry configured to control the first inner fine actuator of a first inner actuator arm to actuate the top head of the first inner actuator arm in a first radial direction and concurrently control the second inner fine actuator of the first inner actuator arm to actuate the bottom head of the first inner actuator arm in a second radial direction opposite the first radial direction.
 2. The data storage device as recited in claim 1, wherein: the first inner fine actuator of the first inner actuator arm has a first electrical orientation and the second inner fine actuator of the first inner actuator arm has a second electrical orientation that is flipped relative to the first electrical orientation; and the control circuitry is further configured to control the first inner fine actuator of the first inner actuator arm to actuate the top head of the first inner actuator arm in the first radial direction and concurrently control the second inner fine actuator of the first inner actuator arm to actuate the bottom head of the first inner actuator arm in the second radial direction opposite the first radial direction by concurrently applying a control signal to the first inner fine actuator and the second inner fine actuator of the first inner actuator arm.
 3. The data storage device as recited in claim 1, wherein: the first outer fine actuator of the first outer actuator arm has a first electrical orientation and the second outer fine actuator of the second outer actuator arm has a second electrical orientation that is flipped relative to the first electrical orientation; and the control circuitry is further configured to control the first outer fine actuator of the first outer actuator arm to actuate the top head of the first outer actuator arm in a first radial direction and concurrently control the second outer fine actuator of the second outer actuator arm to actuate the bottom head of the second outer actuator arm in a second radial direction opposite the first radial direction by concurrently applying a control signal to the first outer fine actuator of the first outer actuator arm and the second outer fine actuator of the second outer actuator arm.
 4. The data storage device as recited in claim 1, wherein the control circuitry is further configured to: control the first inner fine actuator of the first inner actuator arm based on first servo data read from the respective top disk surface in order to access the top disk surface using the respective top head of the first inner actuator arm; and concurrently control the first outer fine actuator of the first outer actuator arm based on second servo data read from the respective top disk surface in order to concurrently access the top disk surface using the respective top head of the first outer actuator arm.
 5. The data storage device as recited in claim 1, wherein the control circuitry is further configured to: generate a control signal; and selectively apply the control signal to at least one of the inner fine actuators or to at least one of the outer fine actuators.
 6. The data storage device as recited in claim 5, wherein the control circuitry is further configured to: selectively apply the control signal to at least two of the inner fine actuators or to both of the outer fine actuators.
 7. Control circuitry comprising: instructions that, when executed, are configured to initiate a control signal; a first switch switchable between a first active mode and a first inactive mode, wherein in the first active mode the first switch is configured to apply the control signal to inner fine actuators of inner actuator arms; and a second switch switchable between a second active mode and a second inactive mode, wherein in the second active mode the first switch is configured to apply the control signal to outer fine actuators of outer actuator arms, wherein each inner actuator arm and each outer actuator arm comprises a head configured to access a disk surface of a disk.
 8. Control circuitry comprising: a means for initiating a control signal; a first means for switching between a first active mode and a first inactive mode, wherein in the first active mode the first means is configured to apply the control signal to inner fine actuators of inner actuator arms; and a second means for switching between a second active mode and a second inactive mode, wherein in the second active mode the second means is configured to apply the control signal to outer fine actuators of outer actuator arms, wherein each inner actuator arm and each outer actuator arm comprises a head configured to access a disk surface of a disk.
 9. The data storage device as recited in claim 1, further comprising a coarse actuator configured to concurrently move the inner actuator arms and the outer actuator arms to actuate the heads over respective disk surfaces.
 10. The data storage device as recited in claim 1, wherein: the control circuitry is further configured to control the first inner fine actuator of the first inner actuator arm to actuate the top head in the first radial direction and concurrently control the second inner fine actuator of the first inner actuator arm to actuate the bottom head in the second radial direction opposite the first radial direction by: applying a first control signal to the first inner fine actuator of the first inner actuator arm, and applying a second control signal to the second inner fine actuator of the first inner actuator arm, the second control signal having an opposite polarity of the first control signal.
 11. The control circuitry as recited in claim 7, wherein in the first inactive mode the first switch is configured to direct the control signal to the second switch.
 12. The control circuitry as recited in claim 7, wherein in the second inactive mode the second switch is configured to direct the control signal to the first switch.
 13. The control circuitry as recited in claim 7, wherein in the first active mode of the first switch the control signal drives the inner fine actuators without driving the outer fine actuators.
 14. The control circuitry as recited in claim 7, wherein in the second active mode of the second switch the control signal drives the outer fine actuators without driving the inner fine actuators.
 15. A data storage device comprising: a plurality of disks each comprising a top disk surface and a bottom disk surface; a plurality of inner actuator arms each comprising a first inner fine actuator configured to actuate a top head over one of the top disk surfaces and a second inner fine actuator configured to actuate a bottom head over one of the bottom disk surfaces; a first outer actuator arm comprising a first outer fine actuator configured to actuate a top head over a top disk surface of a top disk; a second outer actuator arm comprising a second outer fine actuator configured to actuate a bottom head over a bottom disk surface of a bottom disk; and control circuitry configured to control the first outer fine actuator of the first outer actuator arm to actuate the top head of the first outer actuator arm in a first radial direction and concurrently control the second outer fine actuator of the second outer actuator arm to actuate the bottom head of the second outer actuator arm in a second radial direction opposite the first radial direction.
 16. The data storage device as recited in claim 15, wherein: the first outer fine actuator of the first outer actuator arm has a first electrical orientation and the second outer fine actuator of the second outer actuator arm has a second electrical orientation that is flipped relative to the first electrical orientation; and the control circuitry is further configured to control the first outer fine actuator of the first outer actuator arm to actuate the top head of the first outer actuator arm in the first radial direction and concurrently control the second outer fine actuator of the second outer actuator arm to actuate the bottom head of the second outer actuator arm in the second radial direction opposite the first radial direction by concurrently applying a control signal to the first outer fine actuator of the first outer actuator arm and the second outer fine actuator of the second outer actuator arm.
 17. The data storage device as recited in claim 15, wherein: the control circuitry is further configured to control the first outer fine actuator of the first outer actuator arm to actuate the top head of the first outer actuator arm in the first radial direction and concurrently control the second outer fine actuator of the second outer actuator arm to actuate the bottom head in the second radial direction opposite the first radial direction by: applying a first control signal to the first outer fine actuator of the first outer actuator arm, and applying a second control signal to the second outer fine actuator of the second outer actuator arm, the second control signal having an opposite polarity of the first control signal. 